[RE-wrenches] ground fault troubleshooting

William Miller william at millersolar.com
Mon Sep 6 20:46:58 PDT 2010


Colleagues:

I have been saying for some time that we need to rethink PV ground fault 
indicator systems.  The fundamentals of existing GFI systems is for the 
bond between the grounded-conductor and the  grounding-conductor to be 
opened upon a ground fault.  This bond is important for safety and it is 
ludicrous to open it at the time it is most needed.

There are patents awarded for systems to detect ground faults and then 
disconnect PV source circuits at the source.  This is the best idea I can 
think of at this time.  There are more patents to be had for those that can 
innovate in this area.  Until there are better systems on the market, 
regulators can not require better alternatives.

William Miller




At 01:04 PM 9/6/2010, you wrote:

>Wrenches all,
>
>I 100% second Bill B's comment Correct that... I 200% second it. It should 
>be the law.... "Don't begin to troubleshoot a faulted PV circuit without a 
>reliable DC clamp meter."
>
>The MOST DANGEROUS PV system is a wounded PV system. This includes danger 
>to persons and property. Safely and efficiently troubleshooting a faulted 
>PV circuit requires a voltmeter AND an ammeter. And PPE. And adequate 
>knowledge and understanding of operational and non-operational 
>characteristics of PV systems.
>
>The simple reason for this is that, when one or more circuit conductors 
>are faulted to a short condition, the voltage between the faulted elements 
>is zero. Relying on just a voltage reading to determine whether or not to 
>open a circuit under this condition will result in an arc. The amount of 
>energy in that arc will depend on the amount of available sunlight and the 
>amount of PV that is feeding into it. The amount of potential hazard will 
>correspond to these factors as well.
>
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